The effects on the child of the emotional states of other persons are investigated by naturalistic and experimental procedures. These are studies of children's responses to events of distress (pain, sadness, fear, anger, discomfort). Responding is measured in the child's attending, emotional expression, other overt behavior (e.g., withdrawal, intervention) and verbal expressions. A replication of the longitudinal developmental study (MH-00242-01 to 03) is being carried on with addition of standard cognitive assessments. Thirty-six children (24 in original study, 12 in replication study) are studied over a period of nine months during the second year of life. Daily observational (dictated) reports by mothers and experimentally controlled observations in the home at intervals through the nine months are the data base. The data document progression in acquisition of response patterns indicative of (a) empathic experience, (b) recognition of the separate and different experiences by self and other person, and (c) skills to react overtly in a directed way to the other person's emotions. Children differ in the routes of these acquisitions. Many of the children also develop distinct individualistic response to others' emotions.